import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';

function Square(props) {
    return (
      <button 
        className="square"
        onClick={props.onClick}
      >
        {props.value}
      </button>
    );
  }
  
  class Board extends React.Component {
    renderSquare(i) {
      return (
        <Square 
          value={this.props.squares[i]}
          onClick={() => this.props.onClick(i)}
        />
      );
    }
  
    render() {
      return (
        <div>
          <div className="board-row">
            {this.renderSquare(0)}
            {this.renderSquare(1)}
            {this.renderSquare(2)}
          </div>
          <div className="board-row">
            {this.renderSquare(3)}
            {this.renderSquare(4)}
            {this.renderSquare(5)}
          </div>
          <div className="board-row">
            {this.renderSquare(6)}
            {this.renderSquare(7)}
            {this.renderSquare(8)}
          </div>
        </div>
      );
    }
  }
  
  class Game extends React.Component {
    constructor(props) {
      super(props)
      this.state = {
        history: [
          {
            squares: Array(9).fill(null)
          }
        ],
        stepNumber: 0,
        xIsNext: true
      }
    }

    handleClick(i) {
      const history = this.state.history.slice(0, this.state.stepNumber + 1)
      const current = history[history.length - 1]
      const squares = current.squares.slice()

      if(calculateWinner(squares) || squares[i]) {
        return 
      }

      squares[i] = this.state.xIsNext ? 'X' : 'O';
      this.setState({
        history: history.concat([{
          squares: squares,
        }]),
        stepNumber: history.length,
        xIsNext: !this.state.xIsNext,
      });
    }

    jumpTo(step) {
      this.setState({
        stepNumber: step,
        xIsNext: (step % 2) === 0
      })
    }

    render() {
      const history = this.state.history;
      const current = history[this.state.stepNumber];
      const winner = calculateWinner(current.squares);

      const moves = history.map((step, move) => {
        const desc = move ? 'Go to move #' + move : 'Go to game start'
        return (
          <li key={move}>
            <button onClick={() => this.jumpTo(move)}>{desc}</button>
          </li>
        )
      })

      let status;
      if (winner) {
        status = 'Winner: ' + winner;
      } else {
        status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
      }

      return (
        <div className="game">
          <div className="game-board">
            <Board 
              squares={current.squares}
              onClick={(i) => this.handleClick(i)}
            />
          </div>
          <div className="game-info">
            <div>{status}</div>
            <ol>{moves}</ol>
          </div>
        </div>
      );
    }
  }
  
  // ========================================
  
  ReactDOM.render(
    <Game />,
    document.getElementById('root')
  );

function calculateWinner(squares) {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}
  